The present invention relates to Mobile IP network technology and home address management. More specifically, this invention relates to mechanisms for managing addresses associated with a network prefix via an edge router that serves as a proxy Home Agent for management of the addresses.
Mobile IP is a protocol which allows laptop computers or other mobile computer units (referred to as “Mobile Nodes” herein) to roam between various sub-networks at various locations—while maintaining internet and/or WAN connectivity. Without Mobile IP or a related protocol, a Mobile Node would be unable to stay connected while roaming through various sub-networks. This is because the IP address required for any node to communicate over the internet is location specific. Each IP address has a field that specifies the particular sub-network on which the node resides. If a user desires to take a computer which is normally attached to one node and roam with it so that it passes through different sub-networks, it cannot use its home base IP address. As a result, a business person traveling across the country cannot merely roam with his or her computer across geographically disparate network segments or wireless nodes while remaining connected over the internet. This is not an acceptable state-of-affairs in the age of portable computational devices.
To address this problem, the Mobile IP protocol has been developed and implemented. An implementation of Mobile IP is described in RFC 3344 of the Network Working Group, C. Perkins, Ed., “IP Mobility Support for IPv4,” August 2002. Mobile IP is also described in the text “Mobile IP Unplugged” by J. Solomon, Prentice Hall. Both of these references are incorporated herein by reference in their entireties and for all purposes.
A similar approach has been described in Mobile IP for IPv6. This is described in RFC3775, which is incorporated herein by reference in its entirety and for all purposes. RFC 3775, entitled “Mobility Support in IPv6,” published in June, 2004, by D. Johnson et al discloses a protocol which allows nodes to remain reachable while roaming in IPv6. This RFC defines the entities of Home Agent (HA), Mobile Node (MN) and Correspondent Node (CN), and describes the Mobile IP registration process with reference to an IPv6 environment.
RFC3775 specifies a method for performing registration of a Mobile Node with its Home Agent in IPv6. Specifically, the Mobile Node provides its care-of address (i.e., location on the foreign network) to the Home Agent via a Binding Update message. In contrast to the registration process that is performed via a Foreign Agent in Mobile IPv4, registration is performed via a co-located care-of address of the Mobile Node in Mobile IPv6. In other words, the care-of address is associated with the Mobile Node rather than a separate entity. The Home Agent then sends a Binding Acknowledgement message to the Mobile Node upon successful completion of registration of the Mobile Node with the Home Agent.
The Mobile IP process in a Mobile IP environment are illustrated in FIG. 1. As shown there, a Mobile IP environment 2 includes the internet (or a WAN) 4 over which a Mobile Node 6 can communicate remotely via mediation by a Home Agent 8 and may also include a Foreign Agent 10 in Mobile IPv4. In the absence of a Foreign Agent in a Mobile IPv4 environment, or in a Mobile IPv6 environment in which a Foreign Agent is not implemented, the Mobile Node 6 can obtain a topologically correct IP address (i.e., collocated IP address) and register this IP address with the Home Agent. (In a Mobile IPv6 environment, this is accomplished via an Access Router rather than a Foreign Agent.) Typically, the Home Agent and Foreign Agent are routers or other network connection devices performing appropriate Mobile IP functions as implemented by software, hardware, and/or firmware. A particular Mobile Node (e.g., a laptop computer) plugged into its home network segment connects with the internet through its designated Home Agent. When the Mobile Node roams, it communicates via the internet through an available Foreign Agent in Mobile IPv4 or an Access Point in Mobile IPv6. Presumably, there are many Foreign Agents (or Access Points) available at geographically disparate locations to allow wide spread internet connection via the Mobile IP protocol. Note that it is also possible for the Mobile Node to register directly with its Home Agent.
As shown in FIG. 1, Mobile Node 6 normally resides on (or is “based at”) a network segment 12 which allows its network entities to communicate over the internet 4 through Home Agent 8 (an appropriately configured router denoted R2). Note that Home Agent 8 need not directly connect to the internet. For example, as shown in FIG. 1, it may be connected through another router (a router R1 in this case). Router R1 may, in turn, connect one or more other routers (e.g., a router R3) with the internet.
Now, suppose that Mobile Node 6 is removed from its home base network segment 12 and roams to a remote network segment 14. Network segment 14 may include various other nodes such as a PC 16. The nodes on network segment 14 communicate with the internet through a router which doubles as Foreign Agent 10 (or Access Point). Mobile Node 6 may identify Foreign Agent 10 in Mobile IPv4 or an Access Point in Mobile IPv6 through various solicitations and advertisements which form part of the Mobile IP protocol. When Mobile Node 6 engages with network segment 14 in Mobile IPv4, Foreign Agent 10 relays a registration request to Home Agent 8 (as indicated by the dotted line “Registration”). Similarly, in Mobile IPv6, when the Mobile Node 6 engages with network segment 14, an Access Point relays a Binding Update message to the Home Agent. The Home and Foreign Agents/Access Points may then negotiate the conditions of the Mobile Node's attachment to Foreign Agent 10 (or Access Point). For example, the attachment may be limited to a period of time, such as two hours. When the negotiation is successfully completed, Home Agent 8 updates an internal “mobility binding table” which specifies the care-of address (e.g., a collocated care-of address or the Foreign Agent's IP address) in association with the identity of Mobile Node 6. Further, the Foreign Agent 10 updates an internal “visitor table” in Mobile IPv4, which specifies the Mobile Node address, Home Agent address, etc. In effect, the Mobile Node's home base IP address (associated with segment 12) has been shifted to its care-of address (e.g., Foreign Agent's IP address associated with segment 14 in Mobile IPv4 or a co-located care-of address in Mobile IPv6).
Now, suppose that Mobile Node 6 wishes to send a message to a Correspondent Node 18 from its new location. In Mobile IPv4, a message from the Mobile Node is then packetized and forwarded through Foreign Agent 10 over the internet 4 and to Correspondent Node 18 (as indicated by the dotted line “packet from MN”) according to a standard internet protocol. If Correspondent Node 18 wishes to send a message to Mobile Node—whether in reply to a message from the Mobile Node or for any other reason—it addresses that message to the IP address of Mobile Node 6 on sub-network 12. The packets of that message are then forwarded over the internet 4 and to router R1 and ultimately to Home Agent 8 as indicated by the dotted line (“packet to MN(1)”). From its mobility binding table, Home Agent 8 recognizes that Mobile Node 6 is no longer attached to network segment 12. It then encapsulates the packets from Correspondent Node 18 (which are addressed to Mobile Node 6 on network segment 12) according to a Mobile IP protocol and forwards these encapsulated packets to a “care of” address for Mobile Node 6 as shown by the dotted line (“packet to MN(2)”). The care-of address may be, for example, the IP address of Foreign Agent 10 or a co-located care-of address associated with the Mobile Node 6. Foreign Agent 10 (if present) then strips the encapsulation and forwards the message to Mobile Node 6 on sub-network 14. The packet forwarding mechanism implemented by the Home and Foreign Agents is often referred to as “tunneling.” In the absence of a Foreign Agent, packets are tunneled directly to the Mobile Node 6 collocated care-of address.
RFC 3633, which is incorporated herein by reference for all purposes, discloses a prefix delegation feature. With this feature, a DHCP server may allocate a network prefix rather than a single IP address. Unfortunately, since service providers generally do not want Home Agent functionality to be performed within the customer network, this prefix delegation feature cannot easily be incorporated into a Mobile IP environment.
In view of the above, it would be desirable if the new prefix delegation feature could be implemented in a Mobile IP environment.